Question

How many moles of solute are contained in a 250.0-milliliter solution that has a concentration of 0.85 M?

Answer 1

Answer: Option (b) is the correct answer.

Explanation:

It is known that molarity is the number of moles present in liter of solution.

Mathematically,    Molarity = $\frac{\text{no. of moles}}{\text{volume in liter}}$

It is given that volume is 250 mL or volume in liter will be 0.25 L (as 1 L = 1000 mL) and molarity is given as 0.85 M.

Therefore, calculate the number of moles of the solute as follows.

          Molarity = $\frac{\text{no. of moles}}{\text{volume in liter}}$

                 0.85 M = $\frac{\text{no. of moles}}{0.25 L}$      

                no. of moles = 0.21 mol

Therefore, we can conclude that 0.21 moles of solute are contained in a 250.0-milliliter solution that has a concentration of 0.85 M.

Answer 2

Answer : The correct option is, 0.21 moles

Solution : Given,

Molarity of the solution = 0.85 M = 0.85 mole/L

Volume of solution = 250 ml = 0.25 L     $(1L=1000ml)$

Molarity : It is defined as the number of moles of solute present in one liter of the solution.

Formula used :

$Molarity=\frac{\text{moles of solute}}{\text{Volume of solution in liters}}$

Now put all the given values in this formula, we get the moles of solute of the solution.

$0.85mole/L=\frac{\text{moles of solute}}{0.25L}$

$\text{moles of solute}=0.2125=0.21moles$

Therefore, the moles of solute is, 0.21 moles